When comparing Arc vs Zukitwo, the Slant community recommends Arc for most people. In the question“What are the best Gnome Shell themes?” Arc is ranked 1st while Zukitwo is ranked 5th.
Ranked in these QuestionsQuestion Ranking
Pro Customizable to dark or light themes
Pro Has both GTK2 and GTK 3 support
Users will be able to match their gtk2 and gtk3 themes easily due to Ark supporting both.
Pro Supports gnome-shell
Pro Available firefox and chromium themes
There are matching themes for Firefox and Chromium for those that want to have a fully matched looking environment.
Pro Really clean and nice-looking
Pro Offers PPA for easy install on Ubuntu based distros
Zukitwo offers an Ubuntu PPA for Ubuntu based distros.
sudo add-apt-repository ppa:noobslab/themes sudo apt-get update sudo apt-get install zukitwo
Pro Built in matching GTK theme
Zukitwo theme offers a matching GTK theme to the built in Gnome Shell theme.
Con Bleak font colors that cause eye strain
The font color in Arc and Arc-Darker is not black, but lightgray
after prolonged usage, it becomes apparent that this font color, combined with white backgrounds causes too much eye strain
Con Has some contrast issues
The theme is a low contrast theme so it really depends on the screen brightness if you see borders or the text, some elements don't even have borders - this makes the theme barely usable for portable devices.
Con Only supports latest version of Gnome Shell and GTK
Zukitwo only officially supports the latest release of Gnome Shell and GTK.